EE 101: Brilliant On The Basics of Electrical Engineering

Introduction

The basic fact every EE student needs to know is the “electrical (and electronic) engineering is imagination“. Everything goes on inside your head because most processes are not visible. It is not like construction where you will see the output as the work is done. Same way it is not like chemical reactions you see the results throughout the process. It is straightforward the result behavior that determines whether your engineering work is right or not.

As a EE student, you have to be brilliant on the basics. This helps you to understand the complex subjects, recognize simple details easy to be overlooked and be creative in different ways. No matter how advanced a topic is in the EE field, it all comes down to the basics. Once you understand the basics, you can find diverse methods to achieve the underlying goal. That’s Engineering.

Basic EE Quantities You Must Know

SI units

They are the same ones you know. If you can recall, they were said to be the official system for measurements and any other quantity can be derived from them. For these reasons, you cannot do without them because EE involves several derived quantities. 

Here is the list for the basic quantities which form the SI system.

Electrical Charge

Positive or negative charge is something you will hear a lot. What, then, is a charge and how important is to electrical engineers? 

A Charge is the measure of the amount of electricity that passes through a point in an electric circuit when one ampere flows then it for a second. 

It is measured in coulombs(C) and calculated Q = It

where I is the current in amperes and t is the time in seconds.

You may also look at it from the point of the current. We know current is as a result of the flow of electrons and protons. Therefore, a charge can be defined as the property of the protons and electrons which causes the force of attraction and repulsion between them ( thereby, causing their movement). This particular version gave rise to the terms “positive” and “negative” charges. 

Force

Force is simply the ability of a body to push or pull. The important thing about it is the influence which can be manifested directly or indirectly on another body. 

It is measured in newtons(N) and calculated F = m • a

where m is the mass of the body;  a is the acceleration in the direction of the force.

A unit of force is one newton which is one kilogram meter per squared second. The Earth’s gravitational force on body is what we know as weight.

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Electric current

Current can be defined as the number of charges flowing through a point in an electric circuit per second. Simply put, it is the rate of movement of charge. Since it is an SI unit, you can see it is being explained with a derived quantity Charge. 

It is measured in ampere(A) and calculated I = Q / t 

where Q is the electric charge and t is the time in seconds.

In our field, electric current can be direct or alternating. Each has its unique characteristics and areas of applications. For starters, know that the DC has polarity, i.e positive and negative, while AC is ideally without polarity.

Potential Difference

Think of the structure of the atom. Protons and neutrons are within the atom’s nucleus while electrons are found on the shells outside the nucleus. Atoms are usually electrically neutral because the proton number equals the electron number (neutrons have no charge).

For current to flow, electrons have to move from one atom to another. Electrical Potential (Voltage) is the sort of electrical pressure capable of causing the electrons to move and has to be in a particular direction (this event is the current flow). This is why insulators (materials with their electrons firmly held to the nucleus) requires higher voltages before they can conduct.

In a circuit, voltage is the potential difference between two points causing current to flow, from the point with a higher potential to the one of low potential.

Electromotive force (EMF)

In every electric circuit, there must be a source of electrical energy. This energy is supplied to the charges and, in turn, work is done. The source can be a voltage type and the potential difference between its terminals in the absence of electric current is the emf. 

For instance, a battery when not connected to any circuit has a potential difference between its positive and negative terminals. It is assumed that once it is connected to a circuit, this voltage will supply the energy that drives charges through that circuit.

It is measured in voltage(V) and calculated Emf = Electrical Energy / Charge

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Resistance

We have already explained how current flows. Every material has its own arrangement of atoms within it. Some have structures making it difficult for electrons to displace from one atom to another. Others also easily lose electrons from their atoms. With that in mind, we can assume that how current flows through these materials won’t be the same. 

The property of materials that determines how they impede current flow through them is Resistance. 

Resistance is measured in ohms with the formula 

                       R = V / I  

                               or 

R = (resistivity x length of material) / Cross-sectional Area of the material.

Conductance (G)

Instead of looking at it from the impedance point of view, we can choose to see the property of materials that allow current to flow easily through them. This property is Conductance and it is on the other side of resistance. 

It is measured in Siemens(S) and calculated G = 1 / Resistance 

Energy / Work

We are used to the definition of Energy as the ability to do work. As you may know, there are several forms of energy. In modern EE, you may be interested in all types because the goal is finding means to convert other energy sources into electricity as well as how to use electrical energy to produce other energy forms.

It is measured in joules(J) and the formula depends on the type of energy. For instance, mechanical energy is E = Force x distance.

Power

While energy measures your work, power determines the rate at which the work is done. Like energy, there can be several types of power. 

It is measured in watts(W) and calculated Power = Energy/ time

Inductance 

Inductance is the property of a circuit whereby there is an e.m.f. induced into the circuit by the change of flux linkages produced by a current change.

When the e.m.f. is induced in the same circuit as that in which the current is changing, the property is called self inductance, L. When the e.m.f. is induced in a circuit by a change of flux due to current changing in an adjacent circuit, the property is called mutual inductance, M. 

It is measured in henry(H) and calculated L = – emf / (di/dt)

Capacitance

Capacitance is the ratio of the amount of electric charge stored on a conductor to a difference in electric potential. Just like inductance, there can be self capacitance and mutual capacitance.

Read about Self Capacitance and Mutual Capacitance https://en.m.wikipedia.org/wiki/Capacitance

It is measured in farads(F) and the general formula is C = Q / V.

Flux

Electric flux and magnetic flux are terms you will find throughout your EE career. Flux is the effect emanating from a body. That is why you usually draw lines to represent the influence of the electric field or magnetic field. 

Read more on flux https://en.m.wikipedia.org › wikiFlux – Wikipedia